The Golden Age seems to begin in a somewhat standard fashion - the narrator tells us of a wonderful and exotic island. Soon, though, fantasy elements make their way into the story and internal tales begin to twist and turn around each other, eventually overtaking the original narrative. This makes for fairy-tale like stories that contain within them enough fantasy (and even science fiction, in one substory) to transform the novel into something utterly magical and beautiful.
There are many lovely and quote-worthy sentences in the book (see here), but this one has to be my favorite:
I have noticed that a lot of literary critics are bothered by the mixing of genres; indeed, some of them are so easily offended in this regard that they experience distress when faced with trifles like the use in a passage of fiction of concepts of theory (as if there were some fundamental difference between stories of people, animals, plants and objects on the one hand and stories of concepts of the other). -p. 187